The present invention relates broadly to apparatus for cathode sputtering and more particularly to an improved magnetron cathode sputtering system.
Cathode sputtering is widely used for depositing thin films of material onto substrates. Such a process involves ion bombarding a flat target plate of the material to be sputtered in an ionized gas atmosphere in an evacuable coating chamber in which a controlled vacuum is maintained to cause particles of the target plate material to be dislodged and deposited as a thin film on the substrate being coated. The target plate, to which a layer of the coating material to be sputtered is applied, is generally of elongated, rectangular form, with the substrate to be coated being moved either continuously or intermittently therebeneath. The longitudinal axis of the target plate is transverse to the direction of substrate movement.
In an endeavor to attain increased deposition rates the use of magnetic enhanced cathodes has been proposed. Such cathodes are known as planar magnetron cathodes and customarily include an array of permanent magnets arranged in a closed loop and mounted in a fixed position in relation to the flat target plate. Thus, the magnetic field is caused to travel in a closed loop, commonly referred to as a "race track" which provides the path or region along which sputtering or erosion of the target plate material takes place.
One drawback of the convential flat plate target, however, is that the race track along which sputtering takes place is relatively narrow so that erosion occurs in a relatively narrow ring-shaped region corresponding to the shape of the closed loop magnetic field. As a result, only a relatively small portion of the total target material in the so-called race track region is consumed before the target must be replaced.